JP5601855B2 - Fuel cell stack - Google Patents

Description

The present invention manufactures a solid oxide fuel cell (SOFC) stack having a glass sealant with a considerably smaller TEC compared to other fuel cells before operation on the fuel cell unit and interconnect flat plate constituting the stack. Regarding the method. The gas sealant is provided in the system as a paste or glass fiber sheet having a composition containing CaO—MgO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ . More specifically, the present invention has the composition: SiO ₂ 50-70 wt%, Al ₂ O ₃ 0-20 wt%, CaO 10-50 wt%, MgO 0-10 wt%, (Na ₂ O + K ₂ O) 0-6% by weight, B ₂ O ₃ 0-10 weight%, preferably 3-6 wt%, and _{TiO 2, ZrO 2, F,} P 2 O 5, MoO 3, _{Fe 2 O 3, MnO 2,} La-Sr-MnO perovskite (LSM) and solid oxide fuel obtained by a process comprising the use of a glass sealant with 0-5 wt% of functional elements selected from combinations thereof It relates to a battery stack. The glass sealant is preferably a glass fiber sheet in the form of E-glass.

The SOFC includes an oxygen ion conducting electrolyte, a cathode from which oxygen is reduced, and an anode from which hydrogen is oxidized. The general reaction in SOFC is that hydrogen and oxygen react electrochemically to produce electricity, heat and water. The operating temperature for SOFC is in the range of 600-1000 ° C, often in the range of 650-1000 ° C, and more often in the range of 750-850 ° C. The SOFC generates a voltage of approximately 0.75 V in normal operation. For this purpose, the fuel cells are assembled in a stack, in which the fuel cells are electrically connected via an interconnect plate.

  Such fuel cells are typically constructed with a Y-stabilized zirconia (YSZ) electrolyte and a contact layer to the cathode, anode, and electron conductive interconnect plates. The interconnect usually makes a series connection between the cells and comprises a fuel cell gas supply. In order to avoid mixing of air from the cathode region and fuel from the anode region, it is common to also provide an airtight sealant and they also provide proper coupling between the fuel cell unit and the interconnect plate. Bring. The sealant is thus crucial for the performance, durability and safe operation of the fuel cell stack.

  The SOFC can undergo thermal cycling during operation and thereby be exposed to tensile stress. If the tensile stress exceeds the tensile strength of the fuel cell, the fuel cell will break and the entire fuel cell stack will not function properly. One source of tensile stress in SOFCs stems from differences between the coefficient of thermal expansion (TEC) of battery stack components. The high operating temperature and thermal cycle of the SOFC stack requires that the interconnect plate be made of a material with a TEC similar to the fuel cell unit. Today, it is possible to find a suitable material for an interconnect plate having substantially the same TEC as the battery.

Another source of tensile stress that is more difficult to avoid is due to differences in the TEC of the interconnect plate and the sealant, often the glass sealant, in the fuel cell stack. To eliminate the formation of cracks in fuel cell components, the thermal expansion coefficient (TEC) of the sealant is in the range of 11 × 10 ^{−6 to} 13 × 10 ⁻⁶ K ⁻¹ (25-900 ° C). Or it is usually recognized that the TEC for fuel cells should be addressed. In addition, the sealant must be stable without reacting with other materials and / or ambient gases, for example over 40,000 hours.

Common materials used for hermetic sealants are glasses of various compositions and a lot of research has been devoted to the development of suitable glass compositions:
A number of glass sealants suitable for SOFC are described, including alkali oxide silicate glass, mica glass ceramic, alkaline earth oxide borosilicate / silica borate glass and alkaline earth alumina silicate (Patent Document 1). This citation teaches how to make a glass sealant based on dry glass powder and filler. The TEC of the glass powder can be as small as 7.5 · 10 ⁻⁶ K ⁻¹ , so the filler is added to increase the TEC of the final glass powder, so that it is TEC 9 × 10 ^{−6 to} 13 Make it substantially comparable to the TEC of the interconnect flat plate and fuel cell unit with x10 ^-6 K ^-1 .

A glass-ceramic composition provided as a blend within a specific range of Al ₂ O ₃ , BaO, CaO, SrO, B ₂ O ₃ and SiO ₂ has been described (Patent Document 2). Glass and crystallized (after heat treatment) glass-ceramics exhibit TECs in the range of 7 × 10 ⁻⁶ K ⁻¹ to 13 × 10 ⁻⁶ K ⁻¹ . However, a considerable amount of BaO is required in the glass-ceramic composition to obtain a large TEC. Prior to heat treatment, the glass-ceramic TEC is substantially comparable (within 30% range) to the TEC of other solid ceramic components.

Silica / alumina (SiO ₂ 52 wt%, Al ₂ O ₃ 48 wt%; FIBERFRAX® FFX paper # 300, Toshiba Monofrax, thickness 0.35 mm) As a sealing material for solid oxide fuel cells of ceramic fibers Is described (Non-patent Document 1). This sealant can suppress electrolyte-cracking in the fuel cell, but the gas sealant characteristics are insufficient because gas leakage is detected near the sealant.

SiO ₂ and 58% B ₂ O ₃ to about 9%, a Na ₂ O about 11%, about 6% Al ₂ O _3, about 4% BaO, and ZnO, glasses containing CaO and K ₂ O The use of multilayer seals including the use of materials is disclosed (Patent Document 3).

EP-A-1,010,675 EP-A-1,200,371 US-A-2003 / 0203267

S. Taniguchi et al. Journal of Power Sources 90 (2000) 163-169

It is an object of the present invention to provide a solid oxide fuel cell stack that contains an airtight sealant that does not crack in the cell and has low reactivity with other cell stack components.

  Another object of the present invention is to provide a solid oxide fuel cell stack containing an airtight sealant that allows for faster production of the stack with better thickness tolerance of the sealant across the stack.

  Yet another object of the present invention is to provide a solid oxide fuel cell stack containing an airtight sealant that allows for low conductivity at the stack operating temperature.

These and other objects are solved by the present invention.
Thus, the inventors provide a solid oxide fuel cell stack obtained by a process comprising the following steps:
(a) alternating at least one interconnect plate with at least one fuel cell unit, each fuel cell unit comprising an anode, a cathode and an electrolyte disposed between the anode and the cathode, and the interconnect plate and each fuel By providing a glass sealant between the cell units, a first fuel cell stack assembly is formed, the glass sealant having the following composition:
The SiO ₂ 50-70 wt%, the Al ₂ O ₃ 0-20% by weight, CaO, 10-50 wt%, the MgO 0-10 wt%, 0-6 weight _{(Na 2 O + K 2 O} ) %, the B ₂ O ₃ 0-10 wt%, and _{TiO 2, ZrO 2, F,} P 2 O 5, MoO 3, Fe 2 O 3, MnO 2, La-Sr-MnO perovskite (LSM) and 0-5% by weight of functional elements selected from their combination;
(b) heating the first fuel cell stack assembly to a temperature of 500 ° C. or higher and applying a load pressure of 2 to 20 kg / cm ² to the cell stack so that the first assembly has a thickness of 5-100 μm; Converted to a second assembly having a glass sealant;
(c) Convert the second assembly to the final fuel cell stack assembly by cooling the second assembly of step (b) to a temperature below that of step (b).
The glass sealant preferably contains 3-6% by weight of B ₂ O ₃ .
In step (b), the temperature is preferably 800 ° C. or higher and the load pressure is preferably ² to 10 kg / cm ² . Thus, in a preferred embodiment, we provide a solid oxide fuel cell stack obtained by a process comprising the following steps:

(a) alternating at least one interconnect plate with at least one fuel cell unit, each fuel cell unit comprising an anode, a cathode and an electrolyte disposed between the anode and the cathode, and the interconnect plate and each fuel By providing a glass sealant with the cell unit, a first fuel cell stack assembly is formed, the glass sealant having the following composition:
The SiO ₂ 50-70 wt%, the Al ₂ O ₃ 0-20% by weight, CaO, 10-50 wt%, the MgO 0-10 wt%, 0-6 weight _{(Na 2 O + K 2 O} ) %, B ₂ O ₃ 0-10 wt%, preferably 3-6 wt%, and TiO ₂ , ZrO ₂ , F, P ₂ O ₅ , MoO ₃ , Fe ₂ O ₃ , MnO ₂ , La-Sr— 0-5% by weight of a functional element selected from Mn-O perovskite (LSM) and combinations thereof;
(b) heating the first fuel cell stack assembly to a temperature of 800 ° C or higher and applying a load pressure of 2 to 20 kg / cm ² to the cell stack to make the first assembly 5-100 μm thick; Converted to a second assembly having a glass sealant;
(c) Convert the second assembly to the final fuel cell stack assembly by cooling the second assembly of step (b) to a temperature below that of step (b).
In this specification, the terms “glass sealant” and “hermetic sealant” are used interchangeably.

Figure 7 shows a window of 21 thermal cycles recorded during operation within a 26 day summary period (2 day unit) of a 10-cell stack made according to the present invention. The OCV (open circuit voltage) profile for the mean over a 40 day (5 day unit) period is shown.

The stack of step (c) may be cooled to room temperature, for example. Room temperature (RT) means the ambient temperature at which the first fuel cell stack assembly is manufactured, typically 20-30 ° C.

The first fuel cell stack assembly is heated to a temperature of 800 ° C or higher, for example, 850 ° C, 900 ° C, 950 ° C or higher, and at the same time the cell stack is subjected to a load pressure (clamping pressure) of 2-10 kg / cm ² , It is possible to squeeze the sealant material to form an airtight and dense sealant, preferably by pressing at 4-8 kg / cm ² . Furthermore, the load pressure can be higher than 10 kg / cm ² , for example up to 20 kg / cm ² , for example 14 or 18 kg / cm ² . The temperature in step (b) is preferably in the range of 800-900 ° C. Moreover, instead of heating to 800 ° C or higher, lower temperatures can be used, for example, temperatures in the range of 500-800 ° C such as 550, 600, 650, 700 or 750 ° C. . The sealed porous structure thus obtained makes the sealant less susceptible to leakage. The generated thickness of the sealant is in the range of 5-100 μm, often in the range of 5-50 μm, and more often in the range of 10-35 μm.

In another preferred embodiment, the glass sealant has the following composition:
The SiO ₂ 50-65 wt%, the Al ₂ O ₃ 0-20% by weight, a CaO 15-40 wt%, the MgO 0-10 wt%, 0-6 weight _{(Na 2 O + K 2 O} ) %, B ₂ O ₃ 3-6% by weight, and _{TiO 2, ZrO 2, F,} P 2 O 5, MoO 3, Fe 2 O 3, MnO 2, La-Sr-MnO perovskite (LSM) and 0-5% by weight of functional elements selected from those combinations.

Glass sealant composition, in the absence of Al ₂ O ₃ (0 wt%) good, the glass sealant composition, the Al ₂ O ₃ up to 20 wt%, Al ₂ O _3, for example 10-15 wt% It will be appreciated that inclusion is preferred. Similarly, the glass sealant composition may be free of MgO (0 wt%), but the glass sealant composition preferably contains up to 10 wt% MgO, for example 0.5-4 wt% MgO. Glass sealant composition, in the absence of Na ₂ O + K ₂ O (0 wt%) good, the glass sealant composition, preferably contains a Na ₂ O + K ₂ O up to 6 wt%, not containing containing K ₂ O to Na ₂ O up to 2% by weight (K ₂ O 0 wt%) more preferably that, that does not have to contain Na ₂ O 0. 25-2 wt% K ₂ O Most preferred. The glass composition may be free of B ₂ O ₃ (0 wt%), but B ₂ O ₃ can be as high as 6 wt% or 10 wt%. Glass sealant composition, also selected from _{TiO 2, ZrO 2, F,} P 2 O 5, MoO 3, Fe 2 O 3, MnO 2, La-Sr-MnO perovskite (LSM) and combinations thereof The functional element may be absent (0% by weight), but the glass sealant composition may contain up to 5% by weight of the functional element.

The content of SiO ₂ , Al ₂ O ₃ , CaO and MgO preferably accounts for 85-95% or 87-97% by weight of the glass sealant composition, while Na ₂ O + K ₂ O and B ₂ The content of O ₃ accounts for 3-8% by weight of the glass sealant composition, and TiO ₂ , ZrO ₂ , F, P ₂ O ₅ , MoO ₃ , Fe ₂ O ₃ , MnO ₂ , La-Sr-Mn Functional elements selected from -O perovskite (LSM) and combinations thereof account for 0-5% by weight.

Therefore, the present invention has the composition: SiO ₂ 50-70 wt%, Al ₂ O ₃ 0-20 wt%, CaO 10-50 wt%, MgO 0-10 wt%, (Na ₂ O + K ₂ O) 0-6% by weight, the B ₂ O ₃ 0-10 weight%, preferably 3-6 wt%, and _{TiO 2, ZrO 2, F,} P 2 O 5, MoO 3, Fe 2 O _{3, MnO 2, La-Sr} -MnO perovskite (LSM) and glass having a 0-5% by weight of functional elements selected from combinations thereof, for use as a glass sealant in solid oxide fuel cell stack Include.

More specifically, the present invention also includes: Composition: SiO ₂ 52-56 wt%, Al ₂ O ₃ 12-16 wt%, CaO 16-25 wt%, MgO 0-6 wt% Na ₂ O + K ₂ O 0-6 wt%, B ₂ O ₃ 0-10 wt%, preferably 3-6 wt%, TiO ₂ 0-1.5 wt%, F 0-1 wt% Also included is the use of the glass as a glass sealant in a solid oxide fuel cell stack.

Suitable glass composition: SiO ₂ of 52-62 wt%, the Al ₂ O ₃ 10-15% by weight, a CaO 18-25 wt%, the MgO 0.5-4 wt%, a Na ₂ O 0.25-2 E-glass having a weight percent of B ₂ O ₃ of 3.5-5.5 wt.%, Which corresponds to a low boron E-glass as described in US Pat. No. 7,022,634. Therefore, the present invention also has the following composition: SiO ₂ 52-62 wt%, Al ₂ O ₃ 10-15 wt%, CaO 18-25 wt%, MgO 0.5-4 wt%, Na ₂ O Also encompassed is the use of E-glass having 0.25-2 wt% and B ₂ O ₃ 3.5-5.5 wt% as a glass sealant in a solid oxide fuel cell stack.
Another suitable glass composition: a SiO ₂ 52-62 wt%, the Al ₂ O ₃ 12-16% by weight, a CaO 16-25 wt%, the MgO 0-5% by weight, (Na ₂ O + K ₂ O), 0-2 wt%, the B ₂ O ₃ 0-10% by weight, the TiO ₂ 0-1.5 wt%, the Fe ₂ O ₃ 0.05-0.8 wt%, fluoride 0-1.0 This is equivalent to E-glass corresponding to ASTM standard designation D578-05. Therefore, the present invention also includes the composition: SiO ₂ 52-62 wt%, Al ₂ O ₃ 12-16 wt%, CaO 16-25 wt%, MgO 0-5 wt%, (Na ₂ O + K ₂ O), 0-2 wt%, the B ₂ O ₃ 0-10% by weight, the TiO ₂ 0-1.5 wt%, the Fe ₂ O ₃ 0.05-0.8 weight%, 0-1.0 wt fluoride Also included is the use of the% E-glass as a glass sealant in a solid oxide fuel cell stack.

The inventors have found that the TEC of the part containing the sealant leaks during normal operation and thermal cycling, even though the TEC of the sealant in the first fuel cell stack assembly of step (a) is fairly small. It has been found that it is possible to produce a final fuel cell stack that does not occur and works well together. The sealant appears to remain under compression during the cooling step (c) due to the greater shrinkage between this step in the interconnect plate and the cell. For the interconnector plate and the battery ^{TEC 13.3 · 10 -6 K -1 (} RT-700 ° C), as well as for a glass sealant according to the present invention for forming a 10% have and stack thickness 11-33μm TEC 6 · 10 ^- Calculations based on an elastic fracture mechanics model that takes into account the nonlinearity of the thermal expansion coefficient using ⁶ K ^-1 show that the maximum energy release rate for the glass layer is 20 J / m ² Is close to the maximum battery release rate (18 J / m ² ). Therefore, by forming a very thin glass sealant (11-33 μm), battery cracking does not occur.

More preferably, in the heating step (b), the first fuel cell stack assembly is heated to 850-900 ° C. and maintained at this temperature for a holding time of 2-6 hours. Significant crystallization of the sealant does not occur at these retention times and even after about 10 hours. However, after heating for a long time, for example after about 84 hours at 850 ° C, crystallization occurs and the TEC of the sealant is measured in the range of 25-800 ° C, up to 10x10 ^-6 K ^-1 Surprisingly increases.

The glass sealant may or may not crystallize depending on the temperature and holding time used during the heating step (b). Crystallization is unavoidable during operation for more than 100 hours at any temperature equal to or exceeding 800 ° C. For example, after heat treatment at 800 ° C. for 168 hours, crystallization of the sealant occurs in a composition similar to that obtained at 850 ° C. with a retention time of 84 hours, measured in the range of 25-800 ° C., 10 Generates TEC up to × 10 ^-6 K ^-1 . The crystallization phase of the sealant, especially when using sealants with the E-glass composition as listed above, is the diopside in composition ranging from diopside to wollastonite, anorthite and cristobalite. On the other hand, B ₂ O ₃ may stay in the glass phase. When MgO is present in the glass, diopside (CaMg) Si ₂ O ₆ can crystallize as the first phase. Pseudowollastonite / wollastonite (CaSiO ₃ ) crystallizes around the diopside core. Anorthite CaAl ₂ Si ₂ O ₈ forms a solid solution series with alumite, NaAlSi ₃ O ₈ when Na ₂ O is present in the melt. A limited amount of K ₂ O may also be included. The unexpected large TEC of the crystallized sealant is formed by diopside-wollastonite (TEC approx. 8 · 10 ^-6 K ^-1 ) and cristobalite (TEC approx. 20 · 10 ^-6 K ^-1 ). This may be the result of counteracting the presence of small anorthite (TEC about 5 · 10 ^-6 K ^-1 ).

  The tension that the crystallized sealant applies to the ceramic cell is further reduced and thus reduces the risk of crack formation. Thus, the sealant has a better match with the rest of the fuel cell, particularly the interconnect, and the risk for fuel cell cracking during thermal cycling is further reduced.

To ensure fast crystallization of the sealant, it may be added nucleation elements such Pt, F, and _{TiO 2, ZrO 2, MoO 3} , LSM and Fe ₂ O _3.

The sealant is poor in the alkaline components brought about by the sum Na ₂ O + K ₂ O and is free of BaO. It is desirable that the alkali content of the sealant is low (≦ 2% by weight) because the low alkali content of the sealant ensures that the conductivity is low. In addition, a significant amount of alkaline element is present in the Cr-rich oxide flakes of the interconnect made of chromium-based alloys, Na ₂ CrO ₄ with a melting point of 792 ° C. , K ₂ CrO ₄ with a melting point of 976 ° C. , or at least It is corrosive by forming (Na, K) ₂ CrO ₄ having a melting point of 752 ° C. These components become mobile at 800 ° C. and become conductive when operating at this temperature. In addition, alkali tends to lower the softening temperature of the glass, so to operate at temperatures closer to 800 ° C., it is necessary to have more Na ₂ O or K ₂ O in the glass sealant. Can be. Alkaline earth BaO used to increase TEC in the prior art can also be corrosive to Cr-oxide flakes forming BaCrO ₄ and can generate debonding cracks.
In another embodiment of the invention, the glass sealant in step (a) is provided as a sheet of glass fiber.

The term “glass fiber sheet” as used herein refers to a thickness of 0.10 corresponding to a dense sealant layer of 5-100 μm thickness after being applied in step (a) and processed according to the invention. Specifies a layer of ~ 1.0 mm glass fiber. The fiberglass sheet is preferably fiberglass paper, more preferably E-glass paper such as fiberglass paper, and fiberglass paper is 20-200 g / m ² , preferably 30-100 g / m. ^2, or loaded in an amount ranging for example of 50 to 100 g / m ^2.

The glass fiber sheet preferably contains the fiber in an amount of 100-200 g / m ² facing the battery unit and in an amount of 20-50 or 60 g / m ² facing the interconnect plate. A sheet of glass fibers, and the fiber, corresponding to dense sealant layer having a thickness of about 40 and 20μm after processing in accordance with the present invention, 70-100g / m ² towards the cell, for example in an amount of 100 g / m ² 30-60g / m ² towards the interconnect plate, for example, more preferably in an amount of 50 g / m ^2. The glass fiber sheet is E-glass paper and 70-100 g / m ² , for example, towards the battery unit, corresponding to a dense sealant layer about 40 and 20 μm thick after the fiber is processed according to the invention, eg the amount a and 30-60g / m ² towards the interconnect plate of 100 g / m ^2, for example, is most preferred in an amount of 50 g / m ^2. More specifically, for example, using 80 g / m ² for the battery yields a sealant with a thickness of about 30 μm and using 30 g / m ² for the interconnect plate yields a thickness of about 10 μm. By providing sheets of glass fiber of different thicknesses towards the battery and towards the interconnect plate, excellent sealing of the resulting SOFC stack is achieved.

  Subjecting the sealant as a glass fiber sheet, for example, as a glass fiber gasket, such as E-glass fiber, results in improved thickness tolerances compared to fuel cell stacks where the sealant is provided as a powder and / or paste. The sealant thickness 5-100 μm, preferably 5-50 μm, more preferably 10-40 μm in the final fuel cell stack is kept within a specific narrow range, for example ± 5 μm. In this way, the sealant thickness mismatch between the fuel cell units across the final fuel cell stack is compared to a fuel cell stack that provides the sealant, eg, by conventional spraying or vapor deposition of a slurry or paste made from powder. Eliminate or at least significantly reduce. Furthermore, providing the sealant as a sheet of glass fiber in step (a) is to easily produce a glass powder into a slurry or paste by forming a sealant by simply punching commercially available E-glass fiber paper. That solid oxide fuel cell stacks containing sealants can be made without employing much more costly alternatives such as performing processing steps that are associated with adding or adding fillers to increase the TEC of the sealant to enable.

The glass fiber sheet is a chopped E-glass fiber, eg thickness, corresponding to a sealant thickness of 5-50 μm, often 10-40 μm, more often 10-35 μm, eg 20 μm and especially 11-33 μm in the final fuel cell stack. It may be provided as commercial E-glass in the form of a sheet with a length of 0.10-1.0 mm, preferably 0.3-1.0 mm. Of E- glass fiber sheet, and use thereof (E- glass e.g. 50-100g / m ²⁾ are commercially available, suitable sealant to the fuel cell stack, i.e. to suppress the fuel cell cracking during operation, It represents a simple and inexpensive solution to the problem of providing a sealant that provides gas-tight, battery electrical shielding and exhibits low reactivity with interconnect plates. When E-glass is used as the starting glass material, this E-glass is also preferably provided as a sheet of glass fiber such as E-glass fiber paper. Since E-glass can be delivered as a roll of glass fiber, the shape of the sealant with corresponding holes for the separate passage of fuel or oxidant can be provided efficiently and purposefully by a simple punching method. it can.

In yet another embodiment, a filler in the form of MgO, steel powder, quartz, leucite and combinations thereof is added to the sealant in step (a). A large TEC of filler makes it possible to obtain a TEC corresponding to the interconnect plate, ie a composite glass sealant with 12 · 10 ^-6 -13 · 10 ^-6 K ^-1 .

  In another embodiment, the glass sealant is a paste formed by mixing a binder and an organic solvent with glass powder having the composition of claim 1. The paste is used as a paste to be used in a dispenser for screen printing or to make a sealant.

To produce glass with TEC12 · 10 ^-6 -13 · 10 ^-6 K ^-1 , glass powder may be mixed with fillers in the form of MgO, steel powder, quartz, leucite and combinations thereof. .
Again, whether the glass is provided as a glass fiber sheet or as a paste, according to the present invention, the starting glass fiber material is converted into a dense and thereby gas-tight, ie sealed, final fuel. It is possible to make the glass sealant thin in the battery stack, ie 5-100 μm, often 5-50 μm, preferably 11-33 μm. This is highly desirable because the sealed sealant serves to prevent mixing of fuel at the anode and oxidant at the cathode in adjacent fuel cell units. Sealability is the individual load that is squeezed together by the use of a temperature applied at least equal to the load applied on the cell stack during the heating step (b) and often the glass sealant softening point (above 800 ° C.) during this step. It appears to be the result of complete agglomeration between the fibers. Thereby, a closed pore structure or a dense glass is obtained. The relatively high softening temperature of the sealant (above 800 ° C) means that the sealant maintains a high viscosity, for example 10 ⁹ -10 ¹¹ Pa-s at the operating temperature of the fuel cell stack, for example 750-800 ° C. to enable.

Example 1:
A 300 μm thick anode-supported cell with internal supply and exhaust holes has a demasked contact layer in the manifold region to minimize leakage through these porous structures. A metal gasket frame covered with E-glass fiber paper punched in the same shape on both sides, allowing air from the manifold hole to pass over the cathode and fuel gas over the anode side on both sides of the cell. Put. An interconnect plate with manifold holes is placed above and below the battery and gasket assembly. E-glass paper contains fiber in an amount of 100 g / m ² towards the battery and 50 g / m ² towards the interconnect plate, respectively, according to the invention at a temperature of about 880 ° C. and a load pressure of about Corresponds to dense layers of 40 and 20 μm thickness after treatment at 6 kg / cm ² . When the stack is constructed with 5 cells, the cross leakage between the anode and cathode sides is as low as 0.05% and 0.09% as measured at RT after full thermal cycling in the two stacks. By gas chromatography using a ₂ × N ₂ concentration process in oxygen on the cathode side and measuring the N ₂ molar concentration on the anode side using the same gas pressure on the anode side and cathode side during operation, we have At each process anode, we obtained a N ₂ mol% doubling, which is driven by diffusion through the cell's porous structure (mainly the anode support) It shows that. Increasing the gas pressure on the cathode side had no effect on the cross leakage on the anode side.

The XRD-spector of E-glass shows wollastonite, CaSiO ₃ (diadolite, (Ca, Mg) SiO ₃ also fits the spectrum and its presence depends on the MgO- content of the glass) anorthite (CaAl ₂ Si ₂ O ₈ , which may contain up to 10 mol% NaAlSi ₃ O ₈ ) and cristobalite, (SiO ₂ ).

  Taking out 21 thermal cycles in operation or removing the 10-cell stack for other test equipment (Fig. 1) can be seen on the fuel side of the cell, as can be seen in OCV (Open Circuit Voltage) (Fig. 2). No significant effect on cross leakage between air side. The OCV profile in the flat state of FIG. 2 indicates that the present invention allows the components of the stack containing the sealant to leak during normal operation and thermal cycling by simple means (use of E-glass fiber paper as a glass sealant precursor). It shows that it is possible to produce a final fuel cell stack that works well together without producing In addition, there is no exacerbation reaction between the oxide flakes and the E-glass.

  A similar leveling OCV profile was obtained in the following example:

Example 2:
As in Example 1, but E-glass sealant was impregnated with a slurry containing 20-50% by volume of MgO particles of 1-5 μm size, 3% PVA and 67% ethanol by volume (dip coating or By spray).

Example 3:
As in Example 2: The slurry contains 20-50% by volume of 1-3 μm AISI 316L powder.

Example 4:
As in Example 2: The slurry contains 20-50% by volume of leucite.

Claims (15)

The following steps:
(a) alternating at least one interconnect plate with at least one fuel cell unit, each fuel cell unit comprising an anode, a cathode and an electrolyte disposed between the anode and the cathode, and the interconnect plate and each fuel By providing a glass sealant between the cell units, a first fuel cell stack assembly is formed, the glass sealant having the following composition:
The SiO ₂ 50-70 wt%, the Al ₂ O ₃ 0-20% by weight, CaO, 10-50 wt%, the MgO 0-10 wt%, 0-6 weight _{(Na 2 O + K 2 O} ) %, the B ₂ O ₃ 0-10 wt%, and _{TiO 2, ZrO 2, F,} P 2 O 5, MoO 3, Fe 2 O 3, MnO 2, La-Sr-MnO perovskite (LSM) and 0-5% by weight of functional elements selected from their combination;
(b) heating the first fuel cell stack assembly to a temperature of 500 ° C. or higher and applying a load pressure of 2 to 20 kg / cm ² to the cell stack so that the first assembly has a thickness of 5-100 μm; Converted to a second assembly having a glass sealant;
(c) obtained by a process comprising converting the second assembly to a final fuel cell stack assembly by cooling the second assembly of step (b) to a temperature below that of step (b). Solid oxide fuel cell stack. _2. The solid oxide fuel cell stack according to claim 1, wherein the content of B ₂ O ₃ is ₃ to 6% by weight. 3. The solid oxide fuel cell stack according to claim 1, wherein in step (b), the temperature is 800 ° C. or higher, and the load pressure is 2 to 10 kg / cm ² . The content of SiO ₂ , Al ₂ O ₃ , CaO and MgO accounts for 85-95% by weight of the glass sealant composition, and the content of Na ₂ O + K ₂ O and B ₂ O ₃ is the glass sealant composition And from TiO ₂ , F, ZrO ₂ , P ₂ O ₅ , MoO ₃ , Fe ₂ O ₃ , MnO ₂ , La-Sr-Mn-O perovskite (LSM) and combinations thereof The solid oxide fuel cell stack according to any one of claims 1 to 3, wherein the functional elements to be selected occupy 0-5 wt%. The glass sealant is a glass with composition: a SiO ₂ 52-62 wt%, the Al ₂ O ₃ 10-15% by weight, a CaO 18-25 wt%, the MgO 0.5-4 wt%, 0.25-2 weight Na ₂ O 5. The solid oxide fuel cell stack according to claim 1, which is a glass having 3.5% to 5.5% by weight of B ₂ O ₃ . Glass sealant composition: SiO ₂ 52-62%, Al ₂ O ₃ 12-16%, CaO 16-25%, MgO 0-5%, (Na ₂ O + K ₂ O ) 0-2% by weight, the B ₂ O ₃ 0-10% by weight, the TiO ₂ 0-1.5 wt%, the Fe ₂ O ₃ 0.05-0.8% by weight, F (fluoride) with 0-1.0 The solid oxide fuel cell stack according to any one of claims 2 to 4, wherein the stack is a glass having a glass. The solid oxide fuel cell stack according to any one of claims 1 to 6, wherein the glass sealant in the step (a) is provided as a glass fiber sheet. The glass fiber sheet contains fibers in an amount of 70-100 g / m ² towards the battery and 30-60 g / m ² towards the interconnect plate. A solid oxide fuel cell stack according to 1. The solid oxide fuel cell according to any one of claims 1 to 8, wherein the glass sealant in step (a) is loaded with a filler in the form of MgO, steel powder, quartz, leucite and combinations thereof. stack. A solid oxide fuel cell stack, wherein the glass sealant is a paste formed by mixing a binder and an organic solvent with the glass powder having the composition according to any one of claims 1 to 4. 11. The solid oxide fuel cell stack according to claim 10, wherein the glass powder is mixed with a filler in the form of MgO, steel powder, quartz, leucite and combinations thereof. Composition: The SiO ₂ 52-56 wt%, the _Al 2 _{O 3} 12-16% by weight, a CaO 16-25 wt%, the MgO 0-6 _wt%, 0-6 wt% Na ₂ O + _K 2 O, B ₂ O ₃ 3-6% by weight, the TiO ₂ 0-1.5% by weight, the glass having a F 0-1 wt%, use as a glass sealant in solid oxide fuel cell stack.
Composition: The SiO ₂ 52-62 wt%, the Al ₂ O ₃ 10-15% by weight, CaO 18-25 wt%, the MgO 0.5-4 wt%, 0.25-2 wt% Na ₂ O, B ₂ Use of E-glass with 3.5-5.5 wt% O ₃ as a glass sealant in a solid oxide fuel cell stack. 14. Use according to claim 12 or 13, wherein the glass is provided as a glass fiber sheet. 15. Use according to claim 14, wherein the sheet of glass fiber contains the fiber in an amount of 70-100 g / m ² towards the battery and 30-60 g / m ² towards the interconnect plate.